The present invention relates generally to scanned imaging systems, and more particularly to a charge coupled device (CCD) focal plane array used to encode, time delay and integrate scene image deltas.
Video data acquisition systems typically store received video images in a computer memory, as well as present them on a display. The total image is digitally stored in terms of horizontal projection counts of the image pixels, and vertical projection counts of the image lines. Prior art scanned imaging systems are disclosed in the following U.S. patents, the disclosures of which are incorporated herein by reference:
U.S. Pat. No. 4,497,066 issued to A. Gasparri, Jr.; PA0 U.S. Pat. No. 4,400,728, issued to D. Long; and PA0 U.S. Pat. No. 4,488,778, issued to S. White.
The Gasparri reference discloses a video data acquisition system which digitizes picture images of an article and selects signals within a predetermined amplitude range as representations of pixels of the picture image. The Long reference discloses a video process control system for identifying, inspecting, or measuring machined parts or the like in which each part is placed in the viewing field of a video camera. The White reference discloses an apparatus for determining the spatial coordinates of a workpiece within the field of view of the apparatus.
While the video systems of the above-cited references are exemplary in the art, they are subject to dynamic range limitations. The dynamic range of standard focal plane register arrays is typically from 50 dB to 70 dB. The present invention was intended to provide a video image signal processing system which uses charge coupled devices as the readout portion a focal plane array to increase the dynamic range of scanned imaging systems.
Charge coupled devices are used in electronic circuits to sample analog input signals to provide a series of analog bits to be stored in potential wells created at the surface of a semiconductor and transported along the surface by timing signals. More particularly, these charges constitute minority carriers stored at the silicon-silicon dioxide interface of non-memory capacitors and are transferred from the capacitor to a capacitor or well on the same substrate by manipulating the voltages applied across the capacitor. An excellent example of an electronic use of charge coupled devices is disclosed in U.S. Pat. No. 4,573,177 issued to Kenneth J. Petrosky, the disclosure of which is incorporated by reference.
The use of CCD technology has been adapted to imaging systems as disclosed in U.S. Pat. No. 3,808,435 issued to R. Bate et al; and U.S. Pat. No. 4,064,533 issued to D. Lampe et al, the disclosures of which are incorporated herein by reference. The Bate et al reference discloses a scanned image processing circuit using a charge coupled device and charge transfer device multiplexer. The Lampe et al reference discloses a focal plane processor for moving target imaging which takes two time-displaced snapshots of a scene and then differences the signal levels of corresponding elemental areas of the two snapshots to produce an output representative of the difference.
While the art cited above is instructive, the need remains for a signal processing system which reduces the dynamic range limitations of scanned imaging systems which may occur due to the analog differences between scene pixel amplitudes. The present invention is intended to satisfy that need.